Lettuce Growing Guide

Lactuca sativa

How to Grow: Lettuce is a cool-weather crop that thrives in the temperature range
60-65 degrees F, and if thoroughly hardened, most varieties survive temperatures as
low as 20 degrees F. Cold-adapted varieties survive much lower temperatures. Seed
germinates best at about 75 degrees F. Lettuce seed will germinate at a temperature
as low as 40 degrees F. Early spring plantings should be made as hardened transplants
from seed started one month before setting outdoors. Later plantings can be direct-seeded. Sow seed 1/4" deep and thin to 10-16" apart depending
on the variety. Loose-leaf varieties may be planted more closely but
good air circulation should be maintained around the plants. Soil should be
cool and moist during the germination period.

Germination Notes: If the
temperature exceeds 80 degrees F lettuce will often fail to germinate. Lettuce can be
planted during late summer or early fall while the days are still hot provided
that the seeds are germinated in the refrigerator for 4-6 days. Another method
is to soak seed in 10% bleach for 2 hours at 40-60 degrees F followed by 4 water rinses.
This method enhances both the speed and amount of germination. One more
method is to keep soil cool with burlap or boards; remove cover promptly
after germination to keep grasshoppers and other pests from enjoying the
shaded tender sprouts!

Bolt Resistance: Resistance to bolting is highest
with loose-leaf lettuce, followed in order by romaine, butterhead, and bibb,
and crisphead. Lettuce bolts more readily if exposed to temperatures below
50 degrees F during the 2- to 3-leaf stage (the first three weeks after germination).
Thus, spring lettuce is best started indoors and transplanted out at least 3
weeks after sowing. Before the days become hot, mulch the plants to keep
the root temperature cool. In deep summer heat it's difficult to mature quality lettuce--heads become smaller and less sweet--at that
time of year, cucumber and tomato salads are the easiest!

Harvest and Flavor Notes: The glucose content
of lettuce harvested in the morning may be 2-1/2 times greater than lettuce
harvested in the early afternoon. For best quality and maximum sweetness
harvest by 7-8 am, especially in summer.

Greenhouse Note: Use heat-tolerant, loose leaf or bibb
types.

Insect Pests and Diseases: In the greenhouse, control aphids by means
of ladybugs, sticky yellow traps or by insecticidal soap. Maintain good air
circulation around plants to reduce disease.

Maturity Dates: Dates are from
direct seeding. Subtract 15-20 days for dates from transplanting.

Seed Savers:
Isolate varieties by a minimum of 12' for home use. For pure seed isolate
varieties a minimum of 25-50'.

Extend Your Lettuce Season: Begin lettuce production early and keep
it going later in the season by covering plants with a Reemay blanket
(p. 87). Extend your harvest into early summer with this technique:
plant tall vegetables in north-south rows and plant heat-resistant lettuce
underneath the leaf canopy so that it is shaded during the hottest portion
of the day. Corn planted in rows 4 feet apart or pole beans on a fence
or trellis is ideal. Interplanting lettuce with bush squash also gives good
results. Mulch the lettuce well, keep well watered and enjoy!

Romaine (Cos) Lettuce

Romaine lettuce produces upright, elongated tall heads with thick succulent
ribs and distinctively flavored long thick crinkled leaves. Moderately
tolerant of heat and shade, romaine does best in a loose fertile soil, and
is the most nutritious type of lettuce.

Loose-leaf lettuce is a non-heading type of lettuce, second to romaine in
nutritional value, and generally the easiest type for gardeners to grow. As a
group it is the most forgiving of poor soil, is generally more heat-tolerant,
and contains the largest diversity of attractive heirlooms.

Bibb lettuce is more tolerant of hot weather than crisphead lettuce.
As a group it is best for cooler regions, with some notable exceptions.
Intermediate in nutritional value, it has small loose green heads with
blanched yellow interiors and thin, soft-textured leaves.

Crisphead lettuce is the most popular type, appreciated for its tightly
folded blanched crisp leaves, though less nutritious than other types.
Because it is harder to grow to perfection, we offer varieties that are more
adapted for hot regions. Crisphead lettuce should be set out early in the
season since it requires a long cool season. If heads have not formed
by late spring, shading with cheesecloth or screening is recommended.